<p>A noninterference monitoring and replay mechanism using the recorded execution history of a program to control the replay of the program behavior and guarantee the reproduction of its errors is presented. Based on this approach, a noninterference monitoring architecture has been developed to collect the program execution data of a target real-time software system without affecting its execution. A replay mechanism designed to control the reproduction of the program behavior as well as the examination of the states of the target system and its behavior is presented. The monitoring system has been implemented using a Motorola 68000 computer in a Unix system environment. An example is used to illustrate how the mechanism detects timing errors of real-time software systems.</p>